Support is requested for an international symposium on "The Clinical Usefulness of High-Energy Radiation (6-45 MeV Photons and Electrons) in Cancer Management." The symposium, which will be held on May 22-24 under the sponsorphip of the Radiation Therapy Center of Thomas Jefferson University Hospital, will bring together internationally recognized radiation oncologists, medical physicists and radiation biologists to discuss in depth current practice and needs, dosimetry techniques and clinical results, and paths for future development. Within the next two years, over 100 machines of high-energy capability will be in use in the United States; however, there is little information in the current literature concerning their use. The symposium will serve to fill this void and will offer an opportunity for an exchange of information on various aspects of the use of high-energy, low-LET beams, including physical characteristics, radiobiological considerations, clinical techniques and areas for future development. Each of the 18 participants will present a paper outlining his experience, and ample time will be allotted for discussion. It is hoped that through this forum a consensus can be reached on optimum energy levels and a biophysical model for use with high-energy radiation. It is also hoped that through publication the proceedings of this symposium may be made available to those working in the field of radiation therapy who are unable to attend the symposium.